Presently, general hearing ability tests for hearing-impaired people are for examining a hearing threshold level (a pure-tone threshold) by using an audiometer. The hearing threshold tests can check a minimum audible level for each frequency. However, the mechanism of hearing impairment is complicated, which is considered as causing various changes in auditory property, such as loudness recruitment, spectral/temporal masking increase as well as hearing threshold level decrease (see Non Patent Literature 1).
An example of devices for detecting the above-described auditory property changes is a device that estimates a shape of an auditory filter related closely to spectral masking (see Patent Literature 1).
This device uses a masker which is added with a spectral gap (i.e. silent part generated on a frequency axis) and a probe. After setting presentation levels of the masker and the probe, a width of the spectral gap is gradually increased. While gradually increasing the spectral gap width, it is observed whether or not the probe can be heard. Thereby, a minimum spectral gap width by which the probe is heard is measured. Then, depending on a numeral value of the measured spectral gap width, the shape of the auditory filter is estimated using a conversion formula.
Another disclosed example is a device that measures both spectral masking and temporal masking (see Non Patent Literature 2).
This device uses a masker and a probe which are added with one or both of the spectral gap and the temporal gap (i.e silent part generated on a time axis). After setting a presentation level of the masker, a spectral gap width, and a temporal gap width, it is observed whether or not the probe can be heard while varying the presentation level of the probe. Thereby, a minimum presentation level of the probe by which the probe is heard is measured.